This application is based on and claims priority under 35 U.S.C. xc2xa7119 with respect to Japanese Application No. 2000-263716 filed on Aug. 31, 2000, the entire content of which is incorporated herein by reference.
The present invention generally relates to a gear shifting method and control device for a synchromesh transmission. More particularly, the present invention pertains to a gear shifting control device for judging whether gear clashes are generated during a gear shifting of the synchromesh transmission by an actuator.
Vehicles such as automobiles, buses, trucks driven by engines or motors are provided with transmissions in order to obtain driving force and speed in accordance with driving conditions. Generally, there are transmissions including automatic transmissions (AT), CVT (continuously variable transmission), and manual transmissions (MT).
Manual transmissions include a counter shaft serving as an input shaft, a main shaft serving as an output shaft, a plurality of counter gears, a plurality of idling gears, a sleeve, and a synchromesh mechanism. The counter shaft transmits an input torque of an engine. The main shaft transmits an output torque to a propeller shaft. The plurality of counter gears are fixed on the counter shaft. The plurality of idling gears are idly disposed on the main shaft and are always intermeshed with the counter gears respectively. The sleeve is splined with an outer periphery of a hub unitary rotating with the main shaft and is slidable in the axial direction of the output shaft. The synchromesh mechanism selectively slides the sleeve based on the intentions of a driver and achieves a desired gear shift by synchronizing a rotation of the main shaft and a desired rotation of the idling gears in splined engagement.
In the conventional MT, a clutch operation and a shift operation must be conducted by the driver during a gear shift change. The shift operation has been operated by moving a floor (column) shift lever to a desired position shift. The movement of the shift lever is transmitted to a shift fork disposed on a tip end side of a shift fork shaft and engaged with the sleeve, and thus to slide the sleeve. Input torque-and output torque are synchronized by the sliding of the sleeve in the synchromesh mechanism and thus the desired gear shift is achieved.
In recent years, there has been developed a transmission having a manual transmission structure as a base, wherein the shift operation thereof is conducted by an actuator having hydraulic pressure, air pressure, or electric power as a driving power source in order to reduce operational responsibility of the driver.
Hereinafter, the transmission of this kind will be called an automatic manual transmission. The automatic manual transmission achieves: a complete automatic shift change in accordance with the driving condition by controlling the actuator with a gear shifting control device, or a semiautomatic shift change based on the driver""s intention by manually operating a synchromesh transmission.
As in a conventional manual transmission, the automatic manual transmission of this kind may generate gear clash. One of the causes of the gear clash is that the shift change is effected before synchronization is achieved, due to secular deterioration such as abrasion of the chamfer of the synchromesh mechanism, since this kind of automatic manual transmission shares the structure of the conventional manual transmission. The generation of the gear clash leads to early abrasion of spline and chamfer portions such as a sleeve and a synchronizer ring, which is not favorable from the standpoint of durability.
According to a known gear shifting control device of the automatic manual transmission, the displacement and the speed of the sleeve are controlled so that the shift change is not effected before the achievement of the synchronization. Hence, the generation of gear clash has not been considered in designing.
Shown in FIG. 3(a) is a case where the sleeve does not slide during the synchronization of input and output rotation speeds, and the stroke of the sleeve starts advancing only after the rotational speeds of the input rotation and the output rotation coincide, that is, after the synchronization is completed during a normal shift change in which gear clash is not generated. On the other hand, shown in FIG. 3(b) is a case where the stroke of the sleeve advances despite a lack of complete synchronization, so relative rotation between the input rotation and the output rotation still remains and gear clash is generated. By advancing the sleeve before completion of the synchronization, a clash between a chamfer of the spline provided on the idling gear and a chamfer of the sleeve is generated, and thus the gear clash is presumed to be generated.
In the forgoing explanation, it is mentioned that after synchronization, the input and output rotation speeds coincide. That is because the rotation speed of the input side and the rotation speed of the output side of the synchromesh mechanism are relatively considered.
Accordingly, needless to say, the rotation speeds of the input side and the output side do not agree with each other even after the completion of the synchronization unless converting the values using a deceleration ratio when the input rotation speed and the output rotation speed are measured separately.
In case the driver conducts the shift operation like a conventional manual transmission, the shift change can be manually achieved by avoiding the type of gear shift which causes gear clash. However, concerning the automatic manual transmission, the shift change is automatically performed to repeatedly select the gear shift despite the generation of gear clash unless countermeasures for preventing gear clash are provided. Thus, the durability of the automatic manual transmission is diminished by the gear clash, and the driver is given an unpleasant feeling.
A need thus exists for an improved gear shifting control device for a synchromesh transmission in which a shift change is performed by an actuator that judges whether a gear clash is generated during shift change.
In light of the foregoing, the present invention provides a gear shifting method and control device for a synchromesh transmission which includes a synchromesh mechanism having a sleeve for achieving a predetermined gear shifting by synchronization between an input shaft and an output shaft of the synchromesh transmission, an actuator for moving the sleeve, and a gear clash judging means for judging whether a gear clash is generated in the synchromesh mechanism based on gear shifting progress information for indicating the state of progress of the gear shifting.
If it is determined that gear clashes occur more frequently during a particular shifting mode (e.g. first gear, or second gear, etc.), than a reference value, then that mode can be thereafter skipped, to avoid wear.